Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$132.40	3.773%	$137.3955	$137.40	$137.40	$137.40
Purchase #2	$168.52	6.309%	$179.1519	$179.15	$179.15	$179.20
Purchase #3	$158.90	8.275%	$172.049	$172.05	$172.05	$172.00
Purchase #4	$123.41	4.498%	$128.961	$128.96	$128.95	$129.00
Purchase #5	$146.69	3.662%	$152.0618	$152.06	$152.05	$152.10
Purchase #6	$159.56	10.736%	$176.6904	$176.69	$176.70	$176.70
Purchase #7	$114.37	3.749%	$118.6577	$118.66	$118.65	$118.70
7 purchase totals =	$1,003.85		$1,064.9673	$1,064.97	$1,064.95	$1,065.10